<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<script>
    var apple1 = 1 ;
    var apple2 = 2 ;
    var temp;
    temp = apple1;
    apple1 = apple2;
    apple2 = temp;
    alert(apple1);
    alert(apple2);
    //isNaN()判断非数字
    console.log(isNaN(12));
    console.log(isNaN('大话'));
</script>
<body>
    
</body>
</html>